I scavenged an air ride jump seat out of an International 9670 cabover in the big truck boneyard for mine., Now its smooth sailing all the way
, can't even feel speed bumps now
Wasn't too much fabrication to get it in.
Finding a stock seat that isn't already hammered may be a good trick. All the ones in the boneyards around here are thoroughly trashed ( of course, if the one you have is leaving you picking springs out of yur butt, I guess just about anything would be an improvement ).
Have you checked around to see what it would run to get your seat redone? In some places like CA and TX you can get it done fairly reasonable, but around here, there aren't any upholstery shops anymore except for one high end custom shop, and just about nothing leaves his shop for under $800
--------Robert